1. Technical Field
The present invention relates to an UTP cable, more specifically, an UTP cable in which crosstalk between pairs and alien crosstalk between adjacent cables are prevented to enhance transmission capacity.
2. Related Art
Generally, UTP (Unshielded Twisted Pair) cable which is used for communication cable is fabricated in the following steps: electric wires including conductor such as copper or etc. coated by insulation material are twisted to form pair, then four pairs are collected and coated by insulation material.
As information technology like ATM and Ethernet or the like develops recently, communication cable appears to be more important, and it has been desired to increase the information transmission capacity of the UTP cable, and the communication cable has been developed to increase its information transmission capacity.
In the meanwhile, the communication cable are classified by the identification characters such as category (or Cat.) and number in accordance with its signal transmission capacity under international agreement, wherein the bigger number means the higher transmission capacity.
For example, communication of Cat. 3 can transmit signal of 16 MHz, Cat. 4 can 20 MHz, and Cat. 5 can 100 MHz, wherein the higher modulation frequency is used, the more information can be transmitted.
However, as the higher modulation frequency is used, the noise due to the crosstalk among the cables and change of the impedance in the conducting wires are increased, which results in a problem that the assortment of the signals gets more difficult in the signal receiver.
For this reason, up to recently, the limit of the UTP cable's signal transmission capacity has been seemed to be around 155 Mbps (Megabit per sec).
However, in view of the developing trend of the related technology such as movie transmission technology and etc., the cable which can transmit information in a higher level will be needed in the near future, so that major cable manufacturers and related system manufacturers are competitively investing for satisfying this need.
However, for improvement of the transmission capacity, usually higher frequency is used, and that results in problems of crosstalk in and out of the UTP cable, so it is very important to lessen the crosstalk for improvement of signal transmission capacity.
The crosstalk depends on outer diameter of wire, pitch, and etc., it is very important to tune properly the factors for excellent transmission characteristic.
FIG. 1 is cross sectional view of a conventional UTP cable.
Referring to FIG. 1, the conventional UTP cable comprises plural pairs 2 that is constituted by twisting two wires 1 coated by insulation material to form a pitch, a separator of ‘+” shape for separating the plural pairs from one another, and sheath wrapping the pairs 2 and the separator 3.
Here, in the conventional UTP cable, a spacer 5 for separating the pairs 2 from the sheath 4 by a distance is integrally formed with the sheath 4, and the spacer 5 is protruded to inner side of the sheath 4 for separating the pairs 2 from the sheath 4.
Here, the conventional UTP cable has the following problems, even though it has advantage of effective separating the pairs 2 from the sheath 4.
The UTP cable is manufactured to have different structural condition (diameter of conductor, diameter of wire, pitch, and etc.) of the pairs 2, so the pairs 2 have different electric characteristic from one another, and a pair that has the longest pitch is most strongly influenced by alien crosstalk.
However, in the conventional UTP cable, the pairs 2 are spaced from the sheath with a same distance by the separator 3 and the spacer 5, so effect by pitch difference is not considered for alien crosstalk characteristic.
That is, distances between center of the UTP cable and centers of each pair 2 are all same, regardless of different alien crosstalk characteristic of each pair that has different electric characteristic from one another, crosstalk decrease effect by spacing distance only is expected.
And, for the conventional UTP cable, alien crosstalk is lessened only by size of spacer 5 and spacing distance, so diameter of cable should be larger to minimize the alien crosstalk.
And, undesired spacing distance is occurred to pair with shortest pitch that has relatively good characteristic against alien crosstalk, so manufacturing of UTP cable is ineffective.